A group of US mayors joined forces with survivors of the Tucson gun rampage on Sunday to step up their campaign for tighter gun controls in the wake of the recent mass killing in Aurora, Colorado.

Mayors Against Illegal Guns, the bipartisan coalition of more than 700 mayors including New York's Michael Bloomberg, released a television advertisement during Olympics coverage and the US's top politics shows calling for president Barack Obama and his rival governor Mitt Romney to tackle gun violence.

The ad features survivors of the Tucson shooting in January 2011 that claimed six lives and left another 13 injured, including US representative Gabby Giffords.

"Because 48,000 Americans will be murdered with guns during the next president's term. That's three Aurora shootings every day. We need less silence. And more courage," the survivors say.

"The Tucson survivors have waited nearly 600 days for Washington to take action to end gun violence – they are still waiting, and we are all waiting," said Bloomberg, Mayors Against Illegal Guns' co-chair.

"Every day that goes by without action, 34 more people will be murdered with guns. The people who want to run this country need to tell us their plans to stop the bloodshed."

Boston Mayor Thomas Menino said: "We hope that the demand for a plan to reduce gun violence is heard loud and clear in Washington today. The moment of silence has lasted too long. It's time for real specifics on how we can prevent the gun violence that will claim 48,000 lives in the next presidential term if no action is taken."

In the wake of the Aurora shootings Obama said the Second Amendment right to bear arms was guaranteed but added there should be tighter control of assault rifles like the AR-15 used in the Aurora shooting.

He said: "they belong on the battlefield of war, not on the streets of our cities".

"I believe the majority of gun owners would agree we should do everything possible to prevent criminals and fugitives from purchasing weapons, and we should check someone's criminal record before they can check out a gun seller," he said. He has yet to outline any specific plans.

Romney, who in 2002 supported a ban on assault weapons, said he did not believe changing gun laws would stop tragedies like Aurora. "And so we can sometimes hope that just changing the law will make all bad things go away. It won't. Changing the heart of the American people may well be what's essential, to improve the lots of the American people," he told NBC.

• Editor's note: this article has been corrected to reflect that the gun used in the Aurora shooting was an AR-15, not an AK-15.